Pediatric perforated appendicitis diagnosis based on the C-reactive protein/prealbumin ratio

Pediatric perforated appendicitis, prone to multiple complications, necessitates identifying potential serum biomarkers for early diagnosis and intervention. A cross-sectional study was conducted on patients under 16 with acute appendicitis, admitted to Hainan Women and Children’s Medical Center from January 2019 to July 2023. The patients were categorized into perforated and non-perforated groups. Among the 313 included patients, 106 (33.87%, 95% CI 28.59–39.14%) developed perforation. The C-reactive protein to prealbumin ratio (CPA) showed a significant difference between the perforated and non-perforated groups [6.63 (2.9–13.02) vs. 0.7 (0.11–2.18), p < 0.001]. The AUC of CPA on the ROC curve was 0.691 (95% CI 0.513–0.869, p = 0.084) in patients under 4. In patients aged 4–9, the sensitivity of CPA > 3 predicting perforation was 76.2%, with a specificity of 81.6%, and an AUC of 0.816 (95% CI 0.747–0.886, p < 0.001). For patients aged 9–16, the sensitivity of CPA > 2.2 predicting perforation was 85%, with a specificity of 85.7%, and an AUC of 0.919 (95% CI 0.859–0.979, p < 0.001). CPA > 3 and CPA > 2.2 can predict perforated appendicitis in patients aged 4–9 and 9–16, respectively.


Materials and methods
The study conducted an observational, cross-sectional analysis of data from children diagnosed with acute appendicitis at Hainan Women and Children's Medical Center between January 2019 and July 2023.Inclusion criteria encompassed patients up to 16 years old with acute appendicitis.Exclusion criteria were defined as follows: (1)  patients who did not undergo appendectomy; (2) patients with a pathological diagnosis of chronic appendicitis; (3) patients who received antibiotics before admission.
During the study period, a total of 390 pediatric patients were admitted to the hospital.Out of this cohort, 4 patients did not undergo surgical treatment, 2 had their appendices not located due to severe abdominal

Grouping and perforation definitions
Laparoscopic appendectomy is employed in the management of acute appendicitis in pediatric patients.The cohort was stratified into two categories: perforated appendicitis and non-perforated appendicitis, determined by intraoperative observations and pathological findings.The specific criteria characterizing non-perforated appendicitis encompass congestive, purulent, and gangrenous appendicitis without any discernible macroscopic or microscopic perforation.On the other hand, perforated appendicitis is defined as appendicitis featuring either macroscopic or microscopic perforation.Furthermore, the patient cohort was sub-divided into age-specific groups: below 4 years of age, 4-9 years of age, and 9-16 years of age.This subdivision was undertaken to scrutinize the diagnostic efficacy of CPA across distinct age brackets.

Statistical analysis
Continuous variables are expressed as median and interquartile range (IQR), while categorical variables are presented as counts and percentages.Wilcoxon rank sum tests are applied to continuous variables, and Chisquare tests and Fisher's exact tests are employed for categorical variables, as deemed appropriate.The Friedman test is utilized to ascertain the significance of differences between perforated appendicitis and non-perforated

Informed consent
The patient's guardian consented to the use the patient's blood and tissue samples for clinical research and signed a written informed consent.

Results
The study included a total of 313 children diagnosed with acute appendicitis, comprising 184 males (58.79%).Among them, 106 (33.87%, 95% CI 28.59-39.14%)developed perforated appendicitis.There was no significant difference in sex distribution between the perforated and non-perforated appendicitis groups (p = 0.126), indicating comparable data.Notably, the distribution of perforated appendicitis varied significantly across different age groups (p < 0.001), as illustrated in Fig. 2.
Figure 2. Distribution of non-perforated appendicitis and perforated appendicitis by age group.The distributions of non-perforated appendicitis and perforated appendicitis exhibited significant differences across age groups.In children below 16 years of age, the median age of children with non-perforated appendicitis is 8.42 (6.25-10.83),while the median age of those with perforated appendicitis is 6.29 (4.33-8.75),demonstrating significant differences (p < 0.001).The distributions of non-perforated appendicitis and perforated appendicitis varied significantly across age subgroups (p < 0.001).***Significant differences p < 0.001.

Subgroup analysis
In children below 4 years of age, the perforated appendicitis group exhibits lower levels of hemoglobin, albumin, and prealbumin compared to the non-perforated appendicitis group (p < 0.05).However, the differences in the remaining indicators were not significant between the non-perforated and perforated appendicitis groups (p > 0.05).
In the 9 to 16-year-old age group, there was no significant difference in hemoglobin between the nonperforated and perforated groups (p > 0.05).However, notable variations existed in other indicators (p < 0.001).Particularly, the median CPA for the perforated appendicitis group stood at 8.12 (2.99-15.17),significantly higher than that of the non-perforated appendicitis group (0.62; 0.11-1.8),with a marked significant (p < 0.001).Refer to Table 3 for detailed insights into these findings.
Figure 3 illustrates the distribution of CPA among both the non-perforated and perforated patients within each subgroup.
Table 1.Baseline data on non-perforated and perforated appendicitis.Data is expressed in median and IQR.NLR neutrophil-to-lymphocyte ratio, PLR platelet-to-lymphocyte ratio, CPA C-reactive protein-to-prealbumin ratio.

ROC curve analysis
The ROC curve analysis resulted in an AUC for CPA of 0.691 (95% CI 0.513-0.869,p = 0.084) for children below 4 years old.In the 4 to 9-year-old group, the AUC for CPA was 0.816 (95% CI 0.747-0.886,p < 0.001), indicating an optimal cut-off of 3.0, a sensitivity of 76.2%, and a specificity of 81.6%.Among children aged 9 to 16 years, the AUC for CPA was 0.919 (95% CI 0.859-0.979,p < 0.001), presenting an optimal cut-off of 2.2, a sensitivity of 85%, and a specificity of 85.7%.Details encompassing the ROC curve, cut-off, sensitivity, and specificity are outlined in Table 4.The accuracy in predicting perforated appendicitis in children over 4 years old via CPA appears notably high, as depicted in in Fig. 4.
The study also highlights CPA as a valuable marker for predicting perforated appendicitis in children.CRP, a commonly used marker for inflammatory response, typically rises 4-6 h after infection onset, peaks at 36-72 h, and gradually decreases 4 h after the infection is controlled.This makes it a marker to assess the inflammatory response in acute appendicitis 16 .Prealbumin, an unglycosylated plasma protein synthesized in the liver, is frequently employed to assess recent nutritional status and is considered a "negative acute phase reactant, " reflecting the severity of various acute inflammatory diseases 17 .During perforated appendicitis, the liver's synthesis of prealbumin decreases due to poor protein absorption caused by inflammation, resulting in decreased prealbumin levels 14 .Combined with the aforementioned factors, CPA can provide a more comprehensive reflection of the patient's physiological state of the patient.ROC curve analysis indicates that in children aged 4-9 years, a CPA value greater than 3 serves as a predictor of perforated appendicitis.With an AUC of 0.816, the diagnostic value is high.In children aged 9-16 years, a CPA value greater than 2.2 can effectively predict perforated appendicitis, boasting a high AUC of 0.919, signifying exceptional diagnostic accuracy.Subgroup analysis reveals a significant CPA difference between the perforated and non-perforated groups in children aged above 4 years old.However, in children below 4 years old, CPA may not be applicable for predicting perforated appendicitis, possibly due to their inadequate immune system development and poor response to inflammatory stimuli [18][19][20][21] .These changes underscore the impact of age-related differences in immune system development and physiological characteristics among children 22 .
A META-analysis identifies NLR as a predictor for pediatric acute perforated appendicitis 8 (AUC: 0.86, sensitivity: 82%, specificity: 76%).In a cross-sectional study, both NLR (AUC: 0.74, sensitivity: 77.78%, specificity: 67.14%) and PLR (AUC: 0.74, sensitivity: 77.78%, specificity: 63.57%) serve as predictors 9 .Additionally, a cohort study highlights serum total bilirubin as a potential predictor 10 (AUC: 0.876, sensitivity: 92%, specificity: 77.3%).In comparison to prior research, this study emphasizes the robust predictive value of CPA in pediatric acute perforated appendicitis, particularly in older children, exhibiting higher AUC, sensitivity, and specificity.Table 2. Risk factors for perforated appendicitis.Symptom duration, PLR, and CPA were identified as independent risk factors for perforated appendicitis in the multivariate analysis.NLR neutrophil-tolymphocyte ratio, PLR platelet-to-lymphocyte ratio, CPA C-reactive protein-to-prealbumin ratio, OR odds ratio, CI confidence interval.This study employed subgroup analysis, clearly delineating the characteristics of perforated appendicitis across different age groups.However, due to limitations in sample size, creating too many subgroups would compromise statistical power, leading to the classification of patients into three subgroups.This study excluded patients who received antibiotics before admission, minimizing the impact of antibiotics on changes in inflammatory biomarkers.However, the study has certain limitations.Firstly, the cross-sectional study design complicates the control of pre-admission factors such as medication and diet.Despite efforts to mitigate interfering factors like age, sex, and pre-admission antibiotic use, the results may still be influenced by other unknown factors.Secondly, the relatively small sample size, particularly in the below-4-year-old group, may yield erratic results impacting interpretation and generalization.Additionally, significant differences in fever, platelets, hemoglobin, and other indicators among different subgroups prompt further reflections on changes in patients' physiological and metabolic states.The higher body temperatures may suggest distinct infection-induced inflammatory processes in the immune system of younger patients compared to older patients,although the effects of other unknown factors cannot be Table 3. Perforated and non-perforated appendicitis data by subgroup.The data is expressed in median and IQR.NLR neutrophil-to-lymphocyte ratio, PLR platelet-to-lymphocyte ratio, CPA C-reactive proteinto-prealbumin ratio.*The application of Fisher's exact test.¶ Significant differences between the perforated appendicitis and non-perforated appendicitis subgroups, determined through the Friedman test.ruled out.It's important to note that the study was conducted within a specific medical institution, limiting the generalizability of findings to other regions.Future longitudinal and multicenter studies could further validate these findings, considering variations across regions, healthcare facilities, and populations.
In clinical practice, this study revealed that CPA offers significant predictive value for perforated appendicitis in children aged over 4 years.Importantly, both CRP and prealbumin levels are easily measurable in various medical institutions at relatively low costs.Moreover, the utilization of CPA aids in the early diagnosis of perforated appendicitis, enabling prompt intervention and perioperative management, ultimately contributing to patient safety during and after surgery and promoting a positive prognosis.
In summary, CPA values exceeding 3 and 2.2 serve as predictors of perforated appendicitis in children aged 4-9 years and 9-16 years, respectively.CPA proves to be a valuable tool in effectively discerning the risk of perforation in children with acute appendicitis, offering crucial insights for early clinical intervention.Table 4. CPA cut-off values for predicting perforated appendicitis by age group.The cut-off values of the ROC curves aimed at predicting perforated appendicitis based on the CPA in children aged 4-9 years and those above 9 years were calculated based on the Youden's index (Y), the maximum accuracy (C), the shortest distance in the upper left corner of the ROC curve (D), and the smallest difference between sensitivity and specificity absolute values (S), respectively.In this particular investigation, the D method was chosen to ascertain the optimal cut-off values.CPA C-reactive protein-to-prealbumin ratio.

Figure 1 .
Figure 1.Flowchart of this study.Flowchart of this study, including patient inclusion, exclusion, and grouping.

Figure 4 .
Figure 4. ROC curve of predicting perforated appendicitis in children based on CPA.In children below 4 years of age, the AUC of CPA was 0.691 (95% CI 0.513-0.869,p = 0.084).For children aged 4-9 years, the AUC of CPA increased to 0.816 (95% CI 0.747-0.886,p < 0.001).For children aged 9-16 years, the AUC of CPA further improved to 0.919 (95% CI 0.859-0.979,p < 0.001).Consequently, the accuracy of predicting perforated appendicitis based on CPA demonstrates an increasing trend with the age of the children.CPA C-reactive protein-to-prealbumin ratio, AUC area under the curve.